At present, the secondary battery widely applied in market generally consists of a cell and a casing. The cell is an active component, which is usually formed by stacking or winding of a positive electrode plate, a negative electrode plate and a separator arranged between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive current collector and a positive active material coated on the surface of the positive current collector, the negative electrode plate includes a negative current collector and a negative active material coated on the surface of the negative current collector.
With the commercialization of the secondary cell, the market has much higher requirements on energy density of the cell, as shown in FIG. 1 and FIG. 2, in the interior of the wound cell, the separator needs to be wound individually, totally four layers of separator are successively stacked at the innermost side of the cell, which not only cause a waste of the separator, but also increase the thickness of the cell, thereby the energy density of the cell is reduced. Besides, the electrode tab is provided at the innermost side, i.e., the head portion, of the cell which will cause asymmetry of the cell structure, and lead to cell deformation.
Aiming at the defects of the prior art, the present application is proposed.